Effect of the subjective intensity of fatigue and interoception on perceptual regulation and performance during ...activity, 2022, Greenhouse-Tucknott

Trish · Oct 13, 2023

Effect of the subjective intensity of fatigue and interoception on perceptual regulation and performance during sustained physical activity

Aaron Greenhouse-Tucknott ,

Jake B. Butterworth,

James G. Wrightson,

Neil A. Harrison,

Jeanne Dekerle

Abstract
Background
The subjective experience of fatigue impairs an individual’s ability to sustain physical endurance performance. However, precise understanding of the specific role perceived fatigue plays in the central regulation of performance remains unclear. Here, we examined whether the subjective intensity of a perceived state of fatigue, pre-induced through prior upper body activity, differentially impacted performance and altered perceived effort and affect experienced during a sustained, isometric contraction in lower body. We also explored whether (cardiac) interoception predicted the intensity of experienced perceptual and affective responses and moderated the relationships between constructs during physical activity.

Methods
Using a repeated-measures study design, thirty male participants completed three experimental conditions, with the intensity of a pre-induced state of fatigue manipulated to evoke moderate (MOD), severe (SEV) and minimal (control; CON) intensity of perceptions prior to performance of the sustained contraction.

Results
Performance of the sustained contraction was significantly impaired under a perceived state of fatigue, with reductions of 10% and 14% observed in the MOD and SEV conditions, respectively. Performance impairment was accompanied by greater perceived effort and more negative affective valence reported during the contraction. However, effects were limited to comparisons to CON, with no difference evident between the two experimental trials (i.e. MOD vs. SEV). Individuals’ awareness of their accuracy in judging resting heartbeats was shown to predict the subjective intensity of fatigue experienced during the endurance task. However, interoception did not moderate the relationships evident between fatigue and both perceived effort and affective valence.

Conclusions
A perceived state of fatigue limits endurance performance, influencing both how effortful activity is perceived to be and the affective experience of activity. Though awareness of interoceptive representations of bodily states may be important to the subjective experience of fatigue, interoception does not modulate the relationships between perceived fatigue and other perceptual (i.e. effort) and affective constructs.

Lou B Lou · Oct 13, 2023

Conclusions
'A perceived state of fatigue limits endurance performance, influencing both how effortful activity is perceived to be and the affective experience of activity. Though awareness of interoceptive representations of bodily states may be important to the subjective experience of fatigue, interoception does not modulate the relationships between perceived fatigue and other perceptual (i.e. effort) and affective constructs.'

Can Anyone make sense of that?

Trish · Oct 13, 2023

This was on healthy male participants. The did a knee extension exercise and rated their effort while doing it. They did it 3 times on different days, with one time as the control, and the other 2 with immediately preceding hand grip exercise to make them feel fatigued before they did the knee extensions.

The idea seems to be if you make people feel fatigued by exercising one part of the body, it makes doing an exercise on another part of the body immediately afterwards seem more of an effort and fail sooner. Making the preliminary hand grip exercise moderate or severe level of difficulty didn't make a difference to the knee exercise.

From the discussion:

The present study demonstrated that both moderate and severe intensity of perceived state of fatigue impaired subsequent performance, exacerbating perceived effort and reduced affective valence during the endurance task. However, these effects did not appear to be sensitive to the intensity of perceived state of fatigue, as evidenced by the absence of differences between the two experimental manipulations
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Several mechanisms accounting for the deleterious effect of prior physical activity on endurance performance in a remote muscle group have been proposed, including neural (e.g. inhibition of descending drive to non-activated muscles), biochemical (e.g. migration of accumulated metabolites) and cognitive factors, though the precise mechanism remains unclear [72]. The present findings appeal to the latter, indicating that higher-order cognitions related to fatigue may exert influence on lower sensory processes independent of overt functional changes [29]. These effects appear relatively potent and may emerge with only a moderate subjective symptoms.
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So they are saying the results of their study indicate that the mechanism is cognitive rather than neural or biochemical.

Here, we demonstrate that perceived fatigue predicts how effortful and how pleasurable activity is experienced to be. Like self-efficacy, a state of perceived fatigue may thus reflect a cognitive factor related to beliefs concerning capacity [14], that shapes how much effort is invested into a task and the aversiveness of ensuing actions [15, 25], which serves to influence physical tolerance.
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Then a very long paragraph I've added breaks to for easier reading that mentions chronic pathological fatigue, so might be of interest to ME.

Lastly, we explored the possibility that one’s interoceptive ability influenced the emergence of the subjective experiences during sustained physical activity and moderated the relationships between fatigue and perceived effort/affective valence.

Drawing upon recent descriptions of chronic, pathological fatigue [22], we have previously proposed that the subjective symptom of fatigue arising from acute physical exertion may do so as a result of continued detection of challenges that undermines the experience of control over the body [79]. These challenges are underpinned by discrepancies between top-down expectations, or predictions, of internal states and the sensory evidence received from the body.

Reduced confidence in held predictions may subsequently result in greater disparity between what the brain predicts the physiological condition of the body to be and its true state, which subsequently alters the processing of error signals, resulting in greater perceived effort [80, 81] and increasingly negative affective states [82].

Under this framework, we provide a theoretical account of not only how the perception of fatigue emerges during acute physical activity, but also why subsequent activity may be perceived to be more effortful and less pleasurable than normal. The subjective experience of fatigue is offered as an experience emerging from higher-order, metacognitive processing [22] and closely aligned to changes in the estimated precision of descending efferent predictions [79].

In line with this proposition, interoceptive awareness (a measure of an individual’s meta-awareness of interoceptive signals) predicted RoF during the endurance task. Specifically, the greater one’s interoceptive awareness, the lower the subjective experience of fatigue reported during the endurance task across all three trials. The measure of interoceptive awareness used in the present study is cited as a stable representation of ‘error awareness’, that may be generalisable across interoceptive axes [83].

The results indicate that the greater the awareness of internal body representations, which one may assume suggests greater confidence in interoceptive predictions of internal states, the smaller or less reliable prediction error is believed to be, resulting in an attenuated experience of fatigue. Importantly, this was evident for perceived fatigue only, with neither effort nor affective valence related to any dimension of interoception.

This conforms with previous studies examining cardiac interoception on perceived effort [84] and affective valence [85] during physical activity. Indeed, though we were unable to disassociate constructs based on their relationship to performance, this finding indicates that the studied constructs may involve different circuitry, with metacognition playing an important role specifically in the experience of fatigue.
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rvallee · Oct 13, 2023

Not much to do with that, unfortunately. It can mostly be summed as: medicine has no idea what fatigue is or how to define it, and that's the state we are still in.

They tried comparing 'interoception' ability, defined as being able to match perception of heart beat, with fatigue perception. I don't know how that's any relevant, being able to feel one's heart beat does not translate to the full experience of interoception. So this part is pretty much useless, even though it's basically the go-to for everything psychosomatic. There are so many variables that can influence this sensation, and it's such a tiny part of the whole sensory experience.

There is one element that may be of some use, and it's that even with fatigue at its heaviest, objective performance only drops by a maximum of 14%. In healthy people. In this one experiment. For sure the drop in performance for us is massively larger than this, but this makes fatigue especially difficult to study objectively when the differences are so small in actual objective performance. In fact there isn't a strong match between perceived fatigue and actual performance, which makes sense given such a tiny window of difference.

They seem to have a definition of fatigue that is mostly behavioral/motivational, so this is also too reductive and limited in scope. People can be worked to death, in fact routinely are. Especially under threat. They won't perform well, but if the difference is rather small, then it still works out with a large number of people. They are trying to reduce systemic concepts down to single elements but they can't study them in isolation, so it makes no sense at all.

Studies like this make about as much sense as trying to understand quantum mechanics using beakers of liquids in the 17th century. They just don't have the basic knowledge and technology to do anything more than speculate and do very crude experiments. Didn't stop people back then from being convinced they knew almost everything that could ever be known. That is one thing that never changes.

duncan · Oct 13, 2023

This made me think of one of those curious perception tricks, but with eyesight, where you have two identical crescent moon shapes stacked upon one another. One looks bigger than the other. Our perception is fooled.

It's a cool trick, but it has absolutely zero utility in helping diagnose or treat someone with cataracts or failing eyesight.

It's just sleight of hand. It can be amusing, but it needs to be remembered what its real implications are limited to.

Sean · Oct 14, 2023

Drawing upon recent descriptions of chronic, pathological fatigue [22], we have previously proposed that the subjective symptom of fatigue arising from acute physical exertion may do so as a result of continued detection of challenges that undermines the experience of control over the body [79]. These challenges are underpinned by discrepancies between top-down expectations, or predictions, of internal states and the sensory evidence received from the body.
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Love how they are trying to frame this as a new idea, when it is exactly the same basic idea (disrupted interoception) the BPS club have been flogging for decades about ME/CFS, with the FND club getting in on the act more recently.

Under this framework, we provide a theoretical account
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In other words, they have no solid empirical basis for it, so its narrative time!

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Effect of the subjective intensity of fatigue and interoception on perceptual regulation and performance during ...activity, 2022, Greenhouse-Tucknott

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